U.S. patent number 5,419,305 [Application Number 08/116,013] was granted by the patent office on 1995-05-30 for automatic bimetal safety latch for self-cleaning oven doors.
Invention is credited to Roger T. Hanley.
United States Patent |
5,419,305 |
Hanley |
May 30, 1995 |
Automatic bimetal safety latch for self-cleaning oven doors
Abstract
An oven safety door latch has a pair of elongated latch arms
pivotably connected to each other and to a base at a point
intermediate their length. The arms project beyond the base and
have end portions with opposed latching noses. A pawl is rotatably
mounted on the base adjacent an end of the arms and has a blocking
element engageable with the arms. A spring biases the latch arms
and thereby the noses towards each other, and a stop element limits
this movement of the noses towards each other. A thermally
responsive element is operatively connected to the pawl to rotate
it between a first position in which the blocking element is spaced
from the arms, and a second position in which the blocking element
is engaged with the end portions of the arms to limit their
movement and thereby the movement of the noses away from each other
to maintain the latch in engagement with the oven door.
Inventors: |
Hanley; Roger T. (Carroboro,
NC) |
Family
ID: |
22364738 |
Appl.
No.: |
08/116,013 |
Filed: |
September 2, 1993 |
Current U.S.
Class: |
126/197;
126/273R; 292/113; 292/DIG.66; 292/DIG.69 |
Current CPC
Class: |
F24C
15/022 (20130101); Y10S 292/69 (20130101); Y10S
292/66 (20130101); Y10T 292/0917 (20150401) |
Current International
Class: |
F24C
15/02 (20060101); F24C 015/04 () |
Field of
Search: |
;126/197,273
;292/113,DIG.69,DIG.66,105,108 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Iones; Larry
Claims
Having thus described the invention, what is claimed is:
1. An oven safety door latch for use with an oven door having a
pair of horizontally spaced openings on its inner face,
comprising:
(a) a base;
(b) a pair of elongated latch arms pivotably connected to each
other and to said base at a point intermediate their length, one
end of said arms projecting beyond said base, said arms having end
portions at said one end with opposed latching noses;
(c) a pawl rotatably mounted on said base adjacent the other end of
said arms, and having blocking means thereon engageable with the
end portions at said other end of said arms;
(d) biasing means to bias said one end of said latch arms and
thereby said noses towards each other;
(e) limiting means on said base to limit movement of said noses
towards each other; and
(f) a thermally responsive element supported by said base and
operatively connected to said pawl to rotate said pawl between a
first position in which said blocking means is spaced from said
arms, and a second position in which said blocking means is engaged
with said end portions of said arms to limit movement thereof and
thereby to limit movement of said noses away from each other,
whereby closing movement of the associated oven door allows said
noses to be cammed apart by the inner face of the associated door
and to pass through the horizontally spaced openings in the
associated door, said biasing means thereafter biasing said noses
towards each other to lock behind the inner face of the associated
door adjacent the openings therein, subsequent heating of said
thermally responsive element above a preset temperature causing
said pawl to rotate from said first position to said second
position to block movement of said arms and camming apart of said
noses by movement of the door in an opening direction, subsequent
cooling of said thermally responsive element below a preset
temperature causing said pawl to rotate from said second position
to said first position to allow movement of said arms and the
camming apart of said noses upon opening movement of the associated
oven door.
2. The oven safety door latch of claim 1 wherein said blocking
means on said pawl is a tab interposable between said end portions
at said other end of said arms to limit movement thereof towards
each other and thereby to limit movement of said noses away from
each other.
3. The oven safety door latch of claim 2 wherein said biasing means
also biases said end portions at said other end of said arms away
from each other as it biases said one end of said latch arms and
thereby said noses towards each other.
4. The oven safety door latch of claim 1 wherein the biasing means
is a spring engaged with said latch arms intermediate said latching
noses and said point of pivotable connection.
5. The oven safety door latch of claim 4 wherein said spring is a
tension spring having its ends engaged with said arms.
6. The oven safety door latch of claim 1 wherein the limiting means
is a stop element on the base disposed between the pivot point and
said end portions at said one end of said arms.
7. The oven safety door latch of claim 1 wherein said base seats a
pivot pin at said point of pivotal connection, and each of said
arms has an aperture pivotally seating said pin.
8. The oven safety door latch of claim 7 wherein said arms have
overlying horizontally disposed ears and said apertures are
disposed therein.
9. The oven safety door latch of claim 1 wherein said latch
includes temperature setting elements and said preset temperatures
are set by said temperature setting elements engaging said pawl to
limit its rotation.
10. The oven safety door latch of claim 9 wherein said temperature
setting elements are adjustably mounted on said base.
11. The oven safety door latch of claim 1 wherein said thermally
responsive element is a bimetallic coil.
12. An oven safety door latch for use with an oven door having a
pair of horizontally spaced openings on its inner face,
comprising:
(a) a base;
(b) a pair of elongated latch arms pivotably connected to each
other and to said base at a point intermediate their length, one
end of said arms projecting beyond said base, said arms having end
portions at said one end with opposed latching noses;
(c) a pawl rotatably mounted on said base adjacent the other end of
said arms, and having a tab thereon interposable between the end
portions at said other end of said arms;
(d) biasing means to bias said one end of said latch arms and
thereby said noses towards each other and said end portions at said
other end of said arms away from each other;
(e) limiting means on said base to limit movement of said noses
towards each other; and
(f) a thermally responsive element supported by said base and
operatively connected to said pawl to rotate said pawl between a
first position in which said tab is spaced outwardly of said arms,
and a second position in which said tab is interposed between said
end portions to limit movement thereof towards each other and
thereby to limit movement of said noses away from each other,
whereby closing movement of the associated oven door allows said
noses to be cammed apart by the inner face of the associated door
and to pass through the horizontally spaced openings in the
associated door, said biasing means thereafter biasing said noses
towards each other to lock behind the inner face of the associated
door adjacent the openings therein, subsequent heating of said
thermally responsive element above a preset temperature causing
said pawl to rotate from said first position to said second
position to block movement of said arms and camming apart of said
noses by movement of the door in an opening direction, subsequent
cooling of said thermally responsive element below a preset
temperature causing said pawl to rotate from said second position
to said first position to allow movement of said arms and the
camming apart of said noses upon opening movement of the associated
oven door.
13. The oven safety door latch of claim 12 wherein the biasing
means is a spring engaged with said latch arms intermediate said
latching noses and said point of pivotable connection.
14. The oven safety door latch of claim 12 wherein the limiting
means is a stop element on the base disposed between the pivot
point and said end portions at said one end of said arms.
15. The oven safety door latch of claim 12 wherein said base seats
a pivot pin at said point of pivotal connection, and each of said
arms has an aperture pivotally seating said pin.
16. The oven safety door latch of claim 12 wherein said latch
includes temperature setting elements and said preset temperatures
are set by said temperature setting elements engaging said pawl to
limit its rotation.
17. The oven safety door latch of claim 12 wherein said thermally
responsive element is a bimetallic coil.
Description
BACKGROUND OF THE INVENTION
The present invention relates to door latches for ovens and, more
particularly, to automatic safety latches for self-cleaning
ovens.
Many ovens today have a self-cleaning feature allowing for the
complete combustion of organic deposits on the inner walls of the
oven by utilizing temperatures well above the normal range for
cooking.
The use of these high temperatures has made it essential to
maintain the oven door latch in a locked condition when the
temperature is above a preset value. Use of automatic locking
mechanisms protects the user by preventing accidental or
inadvertent opening of the oven door while the temperature is very
high.
In some prior art devices, an external handle is provided on the
oven and is movable to lock the door in a latched condition. A
separate locking mechanism associated with the latching mechanism
is desirably employed to prevent operation of the handle. The
locking means employed in the prior art is usually a rotary thermal
locking member driven by a bimetallic coil, which, upon thermal
expansion, causes rotary motion of the locking member which acts to
prevent operation of the handle to open the oven door.
Several drawbacks exist with this type of locking assembly. The
handle presents an extra manipulation, and in some embodiments
using a bimetallic coil, the locking mechanism does not act
directly upon the latching element. Other prior art devices utilize
a number of interconnected links and locking members, which
increase cost and require more complex mechanisms.
It is an object of the present invention to provide a novel oven
safety door latch which is automatic and simple in operation.
It is also an object to provide such an oven safety door latch in
which the latch arms provide a positive lock for the door through a
simple mechanical action.
Another object is to provide such an oven safety door latch in
which there are relatively few movable parts, which may be
fabricated readily and relatively economically and readily
assembled to provide reliability in operation.
SUMMARY OF THE INVENTION
It has now been found that the foregoing and related objects may be
readily attained in an oven safety door latch for use with an oven
door having a pair of horizontally spaced openings on its inner
face. The latch has a base and a pair of elongated latch arms
pivotably connected to each other and to the base at a point
intermediate their length. One end of the arms projects beyond the
base, and the arms have opposed latching noses on the end portions
at this end.
A pawl is rotatably mounted on the base adjacent the other end of
the arms, and it has blocking means thereon engageable with the end
portions at the other end of the arms. Biasing means biases the one
end of the latch arms and thereby the noses towards each other, and
limiting means on the base limits movement of the noses towards
each other. A thermally responsive element is supported by the base
and operatively connected to the pawl to rotate the pawl between a
first position in which the blocking means is spaced from the arms,
and a second position in which the blocking means is engaged with
the end portions of the arms to limit movement thereof and thereby
to limit movement of the noses away from each other.
Closing movement of the oven door allows the noses to be cammed
apart by the inner face of the door and to pass through its
horizontally spaced openings. The biasing means thereafter biases
the noses towards each other to lock behind the inner face of the
door adjacent the openings therein. Subsequent heating of the
thermally responsive element above a preset temperature causes the
pawl to rotate from the first position to the second position to
block movement of the arms and camming apart of the noses by
movement of the door in an opening direction. Subsequent cooling of
the thermally responsive element below a preset temperature causes
the pawl to rotate from the second position to the first position
to allow movement of the arms and the camming apart of the noses
upon opening movement of the oven door.
Desirably, the blocking means on the pawl is a tab interposable
between the end portions at the other end of the arms to limit
movement thereof towards each other and thereby to limit movement
of the noses away from each other.
Preferably, the biasing means also biases the end portions at the
other end of the arms away from each other as it biases the one end
of the latch arms and thereby the noses towards each other. The
biasing means is usually a tension spring having its ends engaged
with the latch arms intermediate the latching noses and the point
of pivotable connection. The limiting means is a stop element on
the base disposed between the pivot point and the end portions at
the one end of the arms.
In the preferred embodiment, the base seats a pivot pin at the
point of pivotal connection, and each of the arms has an aperture
pivotally seating the pin. The arms have overlying horizontally
disposed ears and the apertures are disposed therein.
The latch includes temperature setting elements adjustably mounted
on the base and the preset temperatures are set by the temperature
setting elements engaging the pawl to limit its rotation. The
thermally responsive element is a bimetallic coil.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top plan view of an oven safety door latch embodying
the present invention;
FIG. 2 is a side elevational view of the oven safety door latch of
FIG. 1 with the oven walls shown fragmentarily in cross section,
the oven door shown fragmentarily in phantom line and the arrow
indicating the direction of closing movement of the oven door;
FIG. 3 is a front elevational view of the oven safety door latch of
FIG. 1;
FIG. 4 is a bottom plan view of the bimetallic coil, housing,
bracket and shaft in the oven safety door latch of FIG. 1;
FIG. 5 is a top plan view of the oven safety door latch of FIG. 1
and of the inner face of a fragmentarily illustrated oven door,
with the door in a partially open position;
FIG. 6 is a similar view showing the oven door camming apart the
latch arms;
FIG. 7 is a similar view with the latch arms engaged with the inner
face of the oven door, but before operation of the thermal locking
mechanism;
FIG. 8 is a similar view after operation of the thermal locking
mechanism to move the locking tab into a blocking position between
the latch arms;
FIG. 9 is a similar view with the thermal locking mechanism having
rotated to again move the locking tab into its position spaced from
the latch arms and with the latch arms being cammed apart to exit
from the inner face of the oven door as the oven door is opened;
and
FIG. 10 is a similar view with all operating elements again in the
disengaged position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning first to FIGS. 1-4, therein illustrated is an oven safety
door latch embodying the present invention with a base or support
generally designated by the numeral 2, a latch assembly generally
designated by the numeral 4, a pawl assembly generally designated
by the numeral 6, a thermally responsive drive assembly generally
designated by the numeral 8, a closed door sensor assembly
generally designated by the numeral 10, and a locked latch sensor
assembly generally designated by the numeral 12.
The base 2 is formed with an upper horizontal portion 14 at its
forward end and a lower parallel portion 16 at the rearward end
joined by a vertical wall 18. The upper portion 14 supports the
latch assembly 4 and the closed door sensor assembly 10. The lower
portion 16 supports the pawl assembly 6, the thermally responsive
drive assembly 8, and the locked latch sensor assembly 12. Edge
portions 20 of the upper portion 14 are bent downwardly and
forwardly to form base legs 22. Portions of the front end of the
upper portion 14 are turned upward at right angles to form mounting
tabs 28.
The latch assembly 4 has elongated latch arms or bolts 30 pivotably
mounted to each other and to the base 2. The latch arms 30 have end
portions 34 at their front end and end portions 38 at their rear
end. The end portions 34 of the latch arms 30 are configured to
provide opposing latching noses 40, and the latch arms 30 have
horizontally disposed ears 42 with aligned apertures therein (not
shown). The ear 42 of the latch arm 30a is offset upwardly to
overlay the ear 42 of the latch arm 30b.
The aligned apertures (not shown) seat the pivot pin or rivet 46
which is secured to the upper portion 14 of the base 2. Also
mounted on the pivot pin 46 below the latch arms 30, is a bushing
48. A bifurcated stop element 24 on the base 2 extends upwardly
between the latch arms 30 and between the pivot pin 46 and the end
portions 34 of the latch arms 30 and limits the movement of the
noses 40 towards each other.
A tension spring 50 is also mounted on the pivot pin 46 above the
latch arms 30 and has downwardly extending end portions 52 engaged
with the latch arms 30 to bias the noses 40 towards a closed
position.
Turning now in detail to the pawl assembly 6, a pawl 54 has an
upstanding locking tab 56 and, adjacent its periphery, an arcuate
slot 58. The periphery of the pawl 54 provides a cam surface 60.
The pawl 54 is mounted to extend parallel to and spaced from the
lower portion 16 of the base 2, and it is supported on the
thermally responsive drive assembly 8.
The pawl assembly 6 also includes a temperature setting element or
lock stop 62 with an arcuate slot 64 which provides an adjustable
orientation of the lock stop 62 on the lower portion 16 by a lock
stop screw 66 slidably positioned within the slot 64. At lease a
portion of the lock stop 62 is positioned between the pawl 54 and
the lower portion 16, and a pair of tabs 68 extend upwardly from
the lock stop 62 into the arcuate slot 58 of the pawl 54.
The thermally responsive drive assembly 8 includes a thermally
responsive element or bimetallic coil 70 spaced below and parallel
to the lower portion 16. A housing 72, open at its bottom, encloses
the bimetallic coil 70, and one end 74 of the bimetallic coil 70 is
attached to the bracket 80. The other end 76 of the bimetallic coil
70 is attached to the shaft 78.
The bracket 80 has an upper horizontal portion 82 affixed to the
lower surface of the lower portion 16 of the base 2. An
intermediate horizontal portion 84 of the thermal bracket 80 is
enclosed within the housing 72 and spaced horizontally above the
bimetallic coil 70. A lower horizontal portion 88 is secured in
heat transfer contact with the top wall of the oven (not
shown).
The intermediate horizontal portion 84 and the upper horizontal
portion 82 have aligned apertures therein (not shown) through which
the shaft 78 extends in a vertical orientation. A thermal lip 92
encloses the portion of the shaft 78 which extends between the
upper horizontal portion 82 and the intermediate horizontal portion
84 of the thermal bracket 80. The shaft 78 passes upward through an
aperture (not shown) in the lower portion 16 of the base 2, and
thence through an aperture (not shown) in the lock stop 62. Mounted
on the shaft 78 above the lock stop 62 are a pawl washer 94 and the
pawl 54. Mounted on the shaft 78 above the pawl 54 are the torque
spring 96, clutch washer 98, and retaining ring 100 which effect
rotation of the pawl 54 when the shaft 78 rotates.
Turning now in detail to the closed door sensor assembly 10, a
sensing plunger 102 is mounted on the pivot pin 46 above and
parallel to the latch arms 30. The sensing pin 102 has a slot 104
which slidingly receives the pivot pin 46, and it passes through a
channel (not shown) in the stop element 24 and has an upturned tab
108 at its back end 109. Mounted on the sensing plunger 102 between
the stop element 24 and a shoulder 107 on the sensing plunger 102
is a compression spring 106.
A microswitch 110 having a switch arm 112 is mounted on the upper
portion 14 of the base 2 by the screws 114, and it is positioned so
that switch arm 112 is adjacent the upturned tab 108 of the sensing
plunger 102 so that it is actuatable thereby.
The locked latch sensor assembly 12 has an insulator 116 mounted on
the lower portion 16 of the base 2, and a second microswitch 118 is
mounted by the screws 114 on the insulator 116 and has an arm 120
positioned adjacent the cam surface 60 of the pawl 54.
Referring now to FIGS. 2 and 5, the oven safety door latch of the
present invention is mounted within the stove so that the latching
noses 40 project therefrom towards the oven door 122. The inner
face 124 of the oven door 122 provides two horizontally spaced
openings 126 through which the latching noses will extend in the
closed position of the door 122, and the arrow 123 shows the
direction of the closing movement of the oven door 122.
The use of the oven safety door latch embodying the principles of
the present invention will be readily apparent. The base 2 of the
oven safety door latch is mounted on a wall of the stove by
fasteners (not shown) extending through the base legs 22, the lower
portion 16 of the base 2, and the mounting tabs 28. The lower
horizontal portion 88 of the bracket 80 may be similarly secured to
the oven wall by fasteners. The bimetallic coil 70 is positioned
adjacent to the oven wall.
Referring now to FIGS. 5-10, the operation of the oven safety door
latch in cooperation with the oven door 122 is illustrated. In FIG.
5, the oven door 122 is in an open position and the latch arms 30
are being biased towards a closed position against the stop element
24 by the spring 50. The tab 56 of the pawl 54 is spaced from the
rear end portions 38 of the latch arms 30. The thermally responsive
drive assembly 8 has not been actuated to rotate the pawl 54 from
its at rest position, and the sensing plunger 102 of the closed
door sensor assembly 10 is biased towards the oven door 122 by the
spring 106. The locked latch sensor assembly 12 is not
actuated.
Referring now to FIG. 6, the oven door 122 has been moved to a
nearly closed position. The latching noses 40 of the latch arm 30
have been cammed apart by the inner face 124 of the oven door 122
and are moving through the horizontally spaced openings 126 of the
inner face 124. The door sensing plunger 102 is in contact with the
oven door 122 but it is not displaced from its forwardly biased
position.
Referring next to FIG. 7, the oven door 122 has been moved to its
closed position, and the latching noses 40 of the latch arms 30 are
lockingly engaged behind the inner face 124 of the oven door 122.
The latching noses 40 have been biased towards this closed position
by the spring 50. The sensing plunger 102 has been moved
rearwardly, causing the upturned tab 108 to bear against the switch
arm 112, thereby activating the microswitch 110. This microswitch
110 can be used to enable the energizing of the oven heating coils
(not shown), a door closed indicator light (not shown), etc.
Referring now to FIG. 8, the oven door 122 and latch assembly 4 are
in the same position as in FIG. 7. However, heating of the oven
above a preset temperature has caused the bimetallic coil 70 to
rotate the shaft 78, thereby rotating the pawl 54 and interposing
the tab 56 between the end portions 38 at the back end of the latch
arms 30. With the tab 56 in this position, the end portions 38 are
prevented from moving further towards each other, thereby
preventing the latching noses 40 from opening if the oven door 122
were pulled in an opening direction. Additionally, rotation of the
pawl 54 has brought the cam surface 60 on the pawl 54 against the
arm 120 of the microswitch 118, which may actuate an indicator
light (not shown) showing that the oven is in the self-cleaning
mode. The closed door sensor assembly 10 continues to be
actuated.
Referring next to FIG. 9, the oven has cooled below a preset
temperature, causing the bimetallic coil 70 to rotate the shaft 78,
thereby locating the tab 56 on the pawl 54 outwardly of the end
portions 38 of the latch arms 30. An opening motion has moved the
oven door 122 into a partially open position by camming apart the
latching noses 40 since the end portions 38 of the latch arms 30
are now able to move towards each other. The partial opening of the
oven door 122 has allowed the sensing plunger 102 to move towards
its forward biased position, thereby deactivating the microswitch
110, and rotation of the pawl 54 has spaced the cam surface 60 from
the arm 120, thereby deactivating microswitch 118.
Referring last to FIG. 10, the oven door 122 has been further
opened, withdrawing the latching noses 40 from the horizontally
spaced openings 126 and allowing them to be biased against the stop
element 24. All other parts are configured as in FIG. 9. As can be
seen from a comparison of FIG. 10 with FIG. 5, the parts are
positioned identically, thereby completing a cycle.
Thus, it can be seen from the foregoing detailed specification and
the attached drawings that the oven safety door latch of the
present invention provides a positive mechanical lock without a
handle, and the two latching noses 40 provide secure latching of
the oven door 122, when the action of the pawl tab 56 on the
latching arms 30 provides a lock for the latching mechanism. The
parts may be readily and relatively economically fabricated and
assembled.
* * * * *